Generally, a horn for a vehicle is provided with a scroll-type or a trumpet-type resonance tube.
For example, in an electrical horn, an oscillation plate oscillates by a solenoid force to generate a sonic wave for oscillating air, and the sonic wave is amplified in a resonance tube. That is, the air oscillation generated by the oscillation plate is transmitted to an exterior of the electrical horn through a sonic passage inside the resonance tube. The resonance tube is a scroll-type resonance tube or a trumpet-type resonance tube, which has an open end portion used as a sonic outlet portion.
The electrical horn is generally attached to a vehicle such that the sonic outlet portion is open toward downwardly, so as to restrict foreign material such as water from entering into the resonance tube from the sonic outlet portion. When the sonic outlet portion is open toward downwardly, a sonic pressure toward a vehicle front side is reduced. Furthermore, even if the sonic outlet portion is open toward downwardly, droplet in vehicle running or water in vehicle washing may be entered into the resonance tube from the sonic outlet portion and may stay in the resonance tube.
JP 2008-89627A proposes an electrical horn configured to reduce the foreign material flowing therein. The electrical horn includes a reflection member configured by a back plate and a bottom plate. The back plate has a through hole and extends to a bottom side of the sonic outlet portion, and the bottom plate extends from the back plate to the vehicle front side, in the reflection member.
In the electrical horn described in JP 2008-89627A, foreign materials flying from the front side moves to the rear side after passing through the through hole of the back plate, and thereby it is necessary to make the through hole to be larger in order to reduce the foreign material staying in the electrical horn. In contrast, the through hole of the back plate needs to be smaller in order to increase the sonic pressure, toward the vehicle front side. That is, the dimension of the through hole has a trade-off relation between an increase of the sonic pressure and a reduction of the foreign material. Therefore, it is difficult to increase the sonic pressure while effectively reducing the foreign material entering into a resonance tube of the electrical horn. Furthermore, the foreign material entering the resonance tube from the sonic outlet portion may flow deeply into the resonance tube. In addition, because the reflection member protrudes downwardly from the sonic outlet portion, the outer dimension of the electrical horn may become larger, and the electrical horn may be difficult to be mounted to a vehicle having a small mounting dimension.